The invention relates generally to control processes and trigger equipment, and more particularly to such processes and equipment for damping resonant oscillations of a parallel-resonant circuit for a pulse-controlled inverter of a current-source inverter, in which the pulse-controlled inverter contains turn-off current-converter switches and is linked to an inductive and to a capacitive load, which form the parallel-resonant circuit.
When a capacitive load is applied electrically parallel to the inductive load of the pulse-controlled inverter of a current-source inverter, a parallel-resonant circuit is formed, whose resonant frequency is a large multiple of the system nominal frequency f.sub.1n. By applying pre-determined modulation modes, such as 3-times pulsation, 5-times pulsation, and 7-times pulsation, the frequency of the fifth or seventh harmonic, and the frequency of the eleventh or thirteenth harmonic, come into the immediate proximity of the resonant frequency f.sub.res of the parallel-resonant circuit in the upper system frequency range. This causes the resonant circuit to be strongly excited, resulting in the load current showing resonant oscillations. Due to these resonant oscillations in the load current, the power loss of the load increases considerably.
The strong excitation of the resonant circuit in the upper system frequency range can be reduced by applying a modulation mode with high pulsation, such as a 13-times pulsation, in the system frequency range. The switching angle and thus the control times are thereby pre-determined in a way which allows the amplitudes of the harmonics to be as small as possible. However, the disadvantage is that for the middle and low system frequency range, the modulation modes show still higher pulsations or that the entire low system frequency range must be controlled asynchronously. In addition, the degree of complexity for pre-determined, optimized pulse patterns rises with the pulse number, as does the power loss of the pulse-controlled inverter.
The present invention is directed to the problem of developing a simple control process for damping these resonant oscillations without increasing the power loss of the pulse-controlled inverter, and to developing a trigger equipment for a pulse-controlled inverter of a current-source inverter, whereby a modulation mode of a lower pulse number can also be applied, particularly in the upper system frequency range without resulting in significant power losses.